1. Field of the Invention
The present invention relates to a power transmitting system of a four-wheel driving vehicle which distributes driving force outputted from a transmission coupled to a laterally mounted front drive engine onto a front wheel and a rear wheel.
2. Description of the Related Art
Conventionally, as a transmission system of a vehicle, particularly, for a four wheel drive vehicle, a coupling mechanism section such as a hydraulic multi plate clutch or a viscous coupling is disposed in a transfer. A distribution of driving force onto a rear wheel is continuously controlled through the coupling mechanism section. Incidentally, in the four wheel drive vehicle in which an engine is laterally arranged, the coupling mechanism section is generally arranged on an axis line of a front wheel driving shaft or on an axis line of a pinion shaft of bevel gears.
For example, in a Japanese Patent Unexamined Publication No. Hei. 7-223455 (JP-A-7-223455), there is disclosed a viscus coupling (coupling mechanism section) which is provided on a side of a differential gear between front wheels, for transmitting a driving force inputted from the differential gear to rear wheels.
In addition, in a Japanese Patent Unexamined Publication No. Hei. 6-107019 (JP-A-6-107019), there is disclosed a hydraulic servo wet type multi plate clutch (coupling mechanism section) which is disposed between an output gear of a hypoid pinion of a transfer unit and a propeller shaft for rear wheel.
However, as described above, in case that the coupling mechanism section is disposed on the axis line of the front wheel driving shaft, a position of the differential gear for being disposed in a transfer is restricted. Further, in some frame structure of a body, when transfer becomes large-sized in a direction of an axle shaft, a mountability thereof is reduced.
While, when the coupling mechanism section is disposed on the axis line of the pinion shaft of the bevel gears, the transfer becomes large-sized in the direction from front to rear. In such case, the coupling mechanism section with a large diameter generally intersect at above or below of a steering gearbox or a body frame structure (cross member etc.). Here, in order to keep a good positional relation among the cross member etc. and coupling mechanism secrion, to change in the position of the steering gear box or to bend the cross member etc. causes a complicated body constitution or an increase in the number of models for vehicles. Moreover, when the coupling mechanism section with a large diameter intersect above or below of the steering gear box or the cross member etc., it causes that a cabin space or a ground clearance of a vehicle is reduced.
Also, a driving force from a transmission coupled to a laterally mounted front drive engine is transmitted, through a gear mechanism including bevel gears such as hypoid gears, to a transmission shaft section such as a propeller shaft longitudinally arranged at a backward of the gear mechanism. From the transmission shaft section, the driving force is transmitted to a final reduction gear unit of rear wheels. Therefore, an output shaft from the gear mechanism is protruded in a backward of the vehicle and coupled to an input shaft of the transmission shaft section.
For example, in a Japanese Patent Unexamined Publication No. Hei. 10-291422 (JP-A-10-291422), there is disclosed a technology in which driving force by a transverse engine is transmitted from a front wheel differential gear unit, through a ring gear and a pinion gear (a pair of bevel gears) as hypoid gears, to an output shaft extending in a backward of the pinion gears. From which output shaft, the driving force is transmitted to a propeller shaft.
Incidentally, in order to transmit the driving force from an engine to rear wheels, it is important for transmittance of the driving force that a steering gear box and body frame members or the like, in front arranged from side to side to the vehicle, are arranged to be prevented from geometrically intersecting mutually. That is, a cabin space, a steering characteristic, a ground clearance etc are strongly depended on the structure to be arranged in such a manner that the driving force is transmitted without being interfered with the steering gear box and body frame members or the like.
In general, in the case of a laterally mounted front drive engine, at immediately backward of the gear mechanism, small diameter portions are provided on each of the output shaft of the gear mechanism and the input shaft of the transmission shaft section so that such objects as a steering gear box and body frame members in front are geometrically avoided. Therefore, it is required that the transmission and gear mechanism are made smallest possible. It is required that the section of the shaft, which have small diameter, is protruded in the backward from a suitable position of the gear mechanism and provided with a small diameter, for avoiding an interference with one another.
In JP-A-10-291422, a pair of the bevel gears are provided, an input shaft section of the propeller shaft is directly coupled to an output shaft extending backward from a pinion gear as a driven gear of the pair of the bevel gears. In such constitution, there is no other gear trains, therefore, the number of parts to be installed can be reduced, and it is advantageous for downsizing.
However, from a view of a positional relation between an outlet position from the bevel gears and the differential gear unit being independent (relation to the position of disposing the propeller shaft), it causes a problem of reducing a degree of design flexibility in making an intersecting axes angle in a universal joint fall within a specified allowed value for suppressing vibration and noise, in the upper and lower sides and in the left and right sides of the vehicle.
In addition, particularly in a four wheel drive vehicle, for designing a vehicle to be a 4WD with functions and performances of the steering gear box and body frame members being made well exhibited, a degree of flexibility is too lowered, since it is necessary to layout a structure in which a transmitting power from a power transfer system between the front and rear wheels to the propeller shaft. This also causes a problem of increasing items to be made compromised.
The present invention has been made in view of foregoing with a first object of providing a power transmitting system of a vehicle, particularly a four wheel drive vehicle in which power transmitting system can be constituted to be compact, and have a good mountability.
Also, the invention has been made in view of foregoing with a second object of providing a power transmitting system of a vehicle which system is small, capable of keeping a good positional relation of a steering mechanism without changing a geometrical arrangement thereof. The power transmitting system of the present invention makes advantageous in suppressing vibration and noise while easily overcoming specified limitations. The present invention produces the power transmitting system easily made to comply with various variation in specification of an engine or a body, and provided with a high degree of flexibility in setting.
In order to solve above problems, according to a first aspect of the present invention, in a power transmitting system of a four wheel drive vehicle, driving force provided from a transmission coupled to a laterally mounted front drive engine is distributed to front and rear wheels through a transfer disposed behind the engine, the transfer comprises a pair of bevel gears which change a transmission direction of the driving force; a first gear provided on a transmission shaft section for the driving force whose transmission direction is changed by the bevel gears; a second gear engaged with the first gear for shifting an axis of the transmission shaft section in parallel to itself; an output shaft which is rotatably inserted into a gear shaft of the second gear, for allowing the driving force to be transmitted to a propeller shaft; and a coupling mechanism section which can control a transmission torque between the gear shaft of the second gear and the output shaft. The coupling mechanism section is disposed on the axis of the second gear more closely to the engine side than the second gear.
In addition, in a power transmitting system of a four wheel drive vehicle, a coupling mechanism-containing chamber for containing the coupling mechanism section is independently provided in a transfer case of the transfer. Liquid tight separation, between the coupling mechanism-containing chamber and other containing chambers containing other parts, is performed by providing a seal member made slidably contacted around the gear shaft of the second gear extendedly provided into the coupling mechanism-containing chamber.
Moreover, in a power transmitting system of a four wheel drive vehicle, a hydraulic multi plate clutch capable to be applied for the coupling mechanism section.
Furthermore, in a power transmitting system of a four wheel drive vehicle, the coupling mechanism section is a coupling which generates a transmission torque depending on a difference between a front wheel rotating speed and a rear wheel rotating speed or on an input torque.
According to a second aspect of the present invention, in a power transmitting system of a vehicle, in which driving force provided from a transmission coupled to a front engine is transmitted through a gear mechanism to a transmission shaft section, the driving force is transmitted from the transmission shaft section to a final reduction gear unit of rear wheels. An axis line of an output shaft of the gear mechanism is arranged to locate one of above and below of members for constituting vehicle, the members being provided from side to side to the vehicle. The output shaft is formed into a hollow shaft with inside face thereof made to be a spline hole. An input shaft of the transmission shaft section is formed into a spline shaf. Here, the output shaft and the input shaft are slidably spline-fitted.
That is, in this power transmitting system of a vehicle, an axis line of an output shaft of the gear mechanism is arranged to locate one of above and below of members for constituting vehicle (hereinafter xe2x80x9cthe vehicle constituting membersxe2x80x9d), the vehicle constituting members being provided from side to side to the vehicle. In this structure, the vehicle constituting members are easily arranged at the optimum position in a wide space. For example, the vehicle constituting members taken as a steering gear box is capable of keeping a good positional relation to the power transmitting system without changing a geometrical arrangement of the steering mechanism. Thus, the power transmitting system can have advantageous in suppressing vibration and noise while easily overcoming specified limitations. In addition, a high degree of flexibility can be kept with respect to a position of arranging the vehicle constituting member, such as the steering gear box, so that the transmission system is allowed to comply with various variations in specification of an engine or a body.
In a power transmitting system of a vehicle, a transaxle is coupled to a laterally mounted front drive engine. A gear mechanism is provided in connection with a front differential gear unit. Here, a power given from the transaxle is transmitted through the gear mechanism to a transmission shaft section. The power is transmitted from the transmission shaft section to a final reduction gear unit of rear wheels. The gear mechanism has bevel gears and helical gears. An axis line of an output shaft of the gear mechanism is arranged to locate one of above and below the vehicle constituting members provided from side to side to the vehicle. The output shaft is formed into a hollow shaft with inside face thereof formed into a spline hole. An input shaft of the transmission shaft section is formed into a spline shaft. The output shaft and the input shaft are slidably spline-fitted.
That is, in this power transmitting system of a vehicle in which a laterally mounted front engine is installed, the axis line of the output shaft of the gear mechanism is arranged to locate one of above and below a vehicle constituting members provided from side to side to the vehicle. In this structure, the vehicle constituting members to be easily arranged at the optimum position in a wide space are allowed. For example, the vehicle constituting members taken as a steering gear box is capable of keeping a good positional relation to the power transmitting system without changing a geometrical arrangement of the steering mechanism. Thus, the power transmitting system have advantageous in suppressing vibration and noise while easily overcoming specified limitations. In addition, a high degree of flexibility can be kept with respect to a position of arranging the vehicle constituting members, such as the steering gear box, so that various variations in specification of an engine or a body capable to be applied are allowed.
Moreover, in a power transmitting system of a vehicle in which a transaxle coupled to a laterally mounted front drive engine is provided, a gear mechanism is provided in connection with a front differential gear unit. A power given from the transaxle is transmitted through the gear mechanism to a transmission shaft section, the power is transmitted from the transmission shaft section to a final reduction gear unit of rear wheels. The gear mechanism has bevel gears and helical gears. At least one of an output shaft of the gear mechanism and an input shaft of the transmission shaft section is formed into a solid shaft. And a flange joint is provided at an end of each of the output shaft and the input shaft. The solid shaft is arranged to locate one of above and below a vehicle constituting members provided from side to side to the vehicle. The output shaft and the input shaft are flange coupled each other at a front side or backward of the vehicle constituting members.
That is, in the power transmitting system of a vehicle with a laterally mounted front drive engine, the solid shaft is arranged to locate one of above and below a vehicle constituting members provided from side to side to the vehicle. In this structure, the diameter of the shaft is made reduced, the shaft being located at least one of above or below the vehicle constituting members. Furthermore, when coupling the output shaft of the gear mechanism and the input shaft of the transmission shaft section with the flange joint, the flange joint having the largest diameter is made located in such a manner that the position of the vehicle constituting members is avoided without interfering with the power transmission. In this structure, the vehicle constituting members such as the steering gear box are allowed to be easily arranged at the optimum position in a wide space. Thus, a good positional relation of a steering mechanism to the power transmitting system can be kept without changing a geometrical arrangement of the steering mechanism, and the power transmitting system is made advantageous in suppressing vibration and noise while easily overcoming specified limitations. In addition, a high degree of flexibility can be kept with respect to a position of arranging the vehicle constituting members such as the steering gear box, so that various variations in specification of an engine or a body are realized.
In addition, the output shaft of the gear mechanism has a helical gear provided around the shaft, the helical gear constituting the gear mechanism. In this structure, the gear mechanism to be further downsized is allowed to large the degree of flexibility in arranging the vehicle constituting members.
Moreover, on the input shaft of the transmission shaft section, a narrowed section with a diameter which corresponding to a shape of the vehicle constituting members is provided so that a transmission strength of transmitted power is ensured. By providing such narrowed section, it becomes possible to avoid vehicle constituting members having various shapes, in positions.
Furthermore, the gear mechanism comprises at least one pair of gears which shifts the output shaft in parallel with itself. In this structure, it is possible that the output shaft of the gear mechanism is freely located, according to the arrangement of the vehicle constituting members. In addition, a gear ratio of the pair of gears is freely determined so that the realization of the optimum power transmission is allowed.